Thermal Conductivity and Thermal Contact Resistance of Metal Foams

2009 ◽  
Author(s):  
Ehsan Sadeghi ◽  
Nedjib Djilali ◽  
Majid Bahrami
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Metal Foam ◽  
Thermal Contact ◽  
High Surface ◽  
Metal Foams ◽  
Analytical Models ◽  
Cross Sectional ◽  
Wide Range

Unique specifications of metal foams such as relatively low cost, ultra-low density, high surface-area-to-volume ratio, and most importantly, the ability to mix the passing fluid provide them a great potential for a variety of thermal-fluidics applications. In the present study, a compact analytical model for evaluating the effective thermal conductivity of metal foams is developed. The medium structure is represented as orthogonal cylindrical ligaments that are equally spaced and sized. A unit cell is taken to represent the metal foam. The model accounts for varying cross-sectional ligaments which is consistent with microscopic images. A numerical analysis is performed to verify the proposed analytical models. The model predictions are in good agreement with existing experimental data and the present numerical results. A parametric study is then performed to investigate the effects of variation in ligament cross-section geometry, uniformity, and aspect ratio over a wide range of porosities. Moreover, Thermal contact resistance phenomenon is included in the analysis.

Thermal Contact Resistance at a Metal Foam-Solid Surface Interface

2011 ◽  
Author(s):  
Ehsan Sadeghi ◽  
Scott Hsieh ◽  
Majid Bahrami
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Effective Thermal Conductivity ◽  
Contact Area ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Metal Foams ◽  
Real Contact Area ◽  
The Real ◽  
Real Contact

Accurate information on heat transfer and temperature distribution in metal foams is necessary for design and modeling of thermal-hydraulic systems incorporating metal foams. The analysis of this process requires determination of the effective thermal conductivity as well as the thermal contact resistance (TCR) associated with the interface between the metal foams and adjacent surfaces/layers. In the present study, a test bed that allows the separation of effective thermal conductivity and thermal contact resistance in metal foams is described. Measurements are performed in a vacuum under varying compressive loads using ERG Duocel aluminum foam samples with different porosities and pore densities. Also, a graphical method associated with a computer code is developed to demonstrate the distribution of contact spots and estimate the real contact area at the interface. Our results show that the porosity and the effective thermal conductivity remain unchanged with the variation of compression in the range of 0 to 2 MPa; but TCR decreases significantly with pressure due to an increase in the real contact area at the interface. Moreover, the ratio of real to nominal contact area varies between 0 to 0.013, depending upon the compressive force, porosity, and surface characteristics.

scholarly journals Effect of Compression on the Effective Thermal Conductivity and Thermal Contact Resistance in PEM Fuel Cell Gas Diffusion Layers

2010 ◽  
Author(s):  
Ehsan Sadeghi ◽  
Ned Djilali ◽  
Majid Bahrami
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Fuel Cell ◽  
Contact Resistance ◽  
Effective Thermal Conductivity ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Analytical Models

Heat transfer through the gas diffusion layer (GDL) of a PEM fuel cell is a key process in the design and operation a PEM fuel cell. The analysis of this process requires determination of the effective thermal conductivity as well as the thermal contact resistance between the GDL and adjacent surfaces/layers. In the present study, a guarded-hot-plate apparatus has been designed and built to measure the effective thermal conductivity and thermal contact resistance in GDLs under vacuum and atmospheric pressure. Toray carbon papers with the porosity of 78% and different thicknesses are used in the experiments under a wide range of compressive loads. Moreover, novel analytical models are developed for the effective thermal conductivity and thermal contact resistance and compared against the present experimental data. Results show good agreements between the experimental data and the analytical models. It is observed that the thermal contact resistance is the dominant component of the total thermal resistance and neglecting this phenomenon may result in enormous errors.

High‐Temperature Skin Softening Materials Overcoming the Trade‐Off between Thermal Conductivity and Thermal Contact Resistance

Small ◽  
2021 ◽  
pp. 2102128
Author(s):  
Taehun Kim ◽  
Seongkyun Kim ◽  
Eungchul Kim ◽  
Taesung Kim ◽  
Jungwan Cho ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Trade Off

Through-Plane Thermal Conductivity of PEMFC Porous Transport Layers

2010 ◽  
Vol 8 (2) ◽  
Author(s):  
Odne S. Burheim ◽  
Jon G. Pharoah ◽  
Hannah Lampert ◽  
Preben J. S. Vie ◽  
Signe Kjelstrup
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Residual Water ◽  
Order Of Magnitude ◽  
Thermal Conductivities

We report the through-plane thermal conductivities of the several widely used carbon porous transport layers (PTLs) and their thermal contact resistance to an aluminum polarization plate. We report these values both for wet and dry samples and at different compaction pressures. We show that depending on the type of PTL and the existence of residual water, the thermal conductivity of the materials varies from 0.15 W K−1 m−1 to 1.6 W K−1 m−1, one order of magnitude. This behavior is the same for the contact resistance varying from 0.8 m2 K W−1 to 11×10−4 m2 K W−1. For dry PTLs, the thermal conductivity decreases with increasing polytetrafluorethylene (PTFE) content and increases with residual water. These effects are explained by the behavior of air, water, and PTFE in between the PTL fibers. It is also found that Toray papers of differing thickness exhibit different thermal conductivities.

scholarly journals Effects of pressure and temperature on thermal contact resistance between different materials

2015 ◽  
Vol 19 (4) ◽  
pp. 1369-1372 ◽  
Author(s):  
Zhe Zhao ◽  
Hai-Ming Huang ◽  
Qing Wang ◽  
Song Ji
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Experimental Approach ◽  
Phenolic Resin ◽  
Thermal Conductivity Coefficient ◽  
Thermal Contact ◽  
Carbon Composites ◽  
Interfacial Temperature ◽  
Temperature And Pressure

To explore whether pressure and temperature can affect thermal contact resistance, we have proposed a new experimental approach for measurement of the thermal contact resistance. Taking the thermal contact resistance between phenolic resin and carbon-carbon composites, cuprum, and aluminum as the examples, the influence of the thermal contact resistance between specimens under pressure is tested by experiment. Two groups of experiments are performed and then an analysis on influencing factors of the thermal contact resistance is presented in this paper. The experimental results reveal that the thermal contact resistance depends not only on the thermal conductivity coefficient of materials, but on the interfacial temperature and pressure. Furthermore, the thermal contact resistance between cuprum and aluminum is more sensitive to pressure and temperature than that between phenolic resin and carbon-carbon composites.

Effective Thermal Conductivity of Composites Reinforced with Curvilinearly Anisotropic Inclusions with Kapitza Contact Resistance

2006 ◽  
Vol 306-308 ◽  
pp. 775-780
Author(s):  
Tung Yang Chen
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Closed Form ◽  
Effective Thermal Conductivity ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Transversely Isotropic ◽  
Closed Form Expression ◽  
Form Expression ◽  
Micromechanical Models

Effective thermal conductivities of composites consisting of curvilinearly anisotropic inclusions with Kapitza thermal contact resistance between the constituents are considered. We show that the effect of these curvilinearly anisotropic inclusions can be exactly simulated by certain equivalent isotropic or transversely isotropic inclusions. Three different micromechanical models are employed to estimate the effective thermal conductivity of the composite. Interestingly, all these methods result in the same simple, closed-form expression.

A Scale Analysis Approach to Thermal Contact Resistance

2003 ◽  
Author(s):  
M. Bahrami ◽  
J. R. Culham ◽  
M. M. Yovanovich
Keyword(s):  
Contact Resistance ◽  
Entire Range ◽  
Thermal Contact Resistance ◽  
Present Model ◽  
Thermal Contact ◽  
Scale Analysis ◽  
Metal Contacts ◽  
Novel Approach ◽  
Wide Range ◽  
Data Points

A new analytical model is developed for predicting thermal contact resistance (TCR) of non-conforming rough contacts of bare solids in a vacuum. Instead of using probability relationships to model the size and number of microcontacts of Gaussian surfaces, a novel approach by employing the “scale analysis methods” is taken. It is shown that the mean size of the microcontacts is proportional to the surface roughness and inversely proportional to the surface asperity slope. A general relationship for determining TCR is derived by superposition of the macro and the effective micro thermal resistances. The present model allows TCR to be predicted over the entire range of non-conforming rough contacts from conforming rough to smooth Hertzian contacts. It is demonstrated that the geometry of heat sources on a half-space for microcontacts is justifiable and that effective micro thermal resistance is not a function of surface curvature. A comparison of the present model with 604 experimental data points, collected by many researchers during the last forty years, shows good agreement for the entire range of TCR. The data covers a wide range of materials, mechanical and thermophysical properties, micro and macro contact geometries, and similar and dissimilar metal contacts.

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